Thermally enhanced cold plate having high conductivity thermal transfer paths

ABSTRACT

A cold plate comprises a cold plate body having a base for thermally engaging a heat-generating device, a plurality of internal channels extending through the cold plate body for the passage of a liquid coolant, a first region between the base and the plurality of internal channels, and a second region between the plurality of internal channels and a top that is generally opposite the base from the plurality of internal channels. The cold plate body is made from a first thermally conductive material. The cold plate also comprises at least one thermally conductive member extending around the plurality of channels from the first region below the plurality of channels to the second region above the plurality of channels. The at least one thermally conductive member has a greater thermal conductivity than the first thermally conductive material to move heat from the first region to the second region.

BACKGROUND

1. Field of the Invention

The present invention relates to cold plates that use a liquid coolantto remove heat from heat-generating devices, such as computerprocessors.

2. Background of the Related Art

Computer systems often rely on cold plates positioned on or nearheat-generating electronic components, such as processors, to maintainperformance of the component by removing heat and thereby maintaining afavorable operating temperature. Cold plates generally use a stream of aliquid coolant to remove the heat that is generated by the electroniccomponent. Cold plate bodies typically have a plurality of liquidcoolant channels there through to maximize heat transfer surface area.With increasing processor power densities, more heat is generated byprocessors that are disposed within the limited space of the computerchassis. It is important for the cold plate to have sufficient capacityto keep the processor cool so that the performance of the processor canbe maintained. However, the cold plate must still fit within theavailable space and form factor of the chassis or server rack.

A cold plate body with a larger overall surface area for heat transferis able to transfer more heat to a liquid coolant flowing through theliquid coolant channels through the cold plate body, but merelyincreasing the size and number of liquid coolant channels yieldsdiminishing returns for the space consumed. Dense electronicconfigurations and increasing processor power densities demand greaterheat transfer capability to maintain processor performance whilecontrolling cold plate cost and weight. For this reason, some coldplates now include heat pipes or vapor chambers in the cold plate base.

BRIEF SUMMARY

One embodiment of the present invention provides a cold plate comprisinga cold plate body having a base for thermally engaging a heat-generatingdevice, a plurality of internal channels extending through the coldplate body for the passage of a liquid coolant, a first region betweenthe base and the plurality of internal channels, and a second regionbetween the plurality of internal channels and a top that is generallyopposite the base from the plurality of internal channels. The coldplate body is made from a first thermally conductive material. The coldplate also comprises at least one thermally conductive member extendingaround the plurality of channels from the first region below theplurality of channels to the second region above the plurality ofchannels. The at least one thermally conductive member has a greaterthermal conductivity than the first thermally conductive material tomove heat from the first region to the second region.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a perspective view of the top of a cold plate that has beenthermally enhanced with high conductivity thermal transfer paths inaccordance with one embodiment of the present invention.

FIG. 1B is a perspective view of the bottom of the cold plate of FIG. 1Ain alignment with a heat-generating processor.

FIG. 2 is a perspective view of an alternative bottom of the cold plateof FIG. 1 in alignment with a heat-generating processor.

FIG. 3 is a schematic side view of the cold plate illustrating the basicflow path of a liquid coolant through the cold plate.

FIG. 4 is a schematic plan view of the cold plate illustrating the flowpath of the liquid coolant through individual channels within the coldplate.

FIG. 5 is a cross-sectional view of the cold plate of FIG. 1, where thecross-section is taken through a central heat pipe.

FIG. 6 is a cross-sectional view of a second embodiment of a cold platehaving a heat pipe that extends completely across the top of the coldplate.

FIG. 7 is a cross-sectional view of a third embodiment of a cold platehaving a heat pipe that is embedded into the cold plate along the bottomof the cold plate, but extends in contact with the outside surface ofthe cold plate along the sides and top of the cold plate.

FIG. 8A is a perspective view of the top of a cold plate that has beenthermally enhanced with high conductivity thermal transfer paths inaccordance with another embodiment of the present invention.

FIG. 8B is a perspective view of the bottom of the cold plate of FIG. 8Ain alignment with a heat-generating processor.

DETAILED DESCRIPTION

Embodiments of the cold plate of the present invention comprise a coldplate body having a base for thermally engaging a heat-generatingdevice, a plurality of internal channels extending through the coldplate body for the passage of a liquid coolant, a first region betweenthe base and the plurality of internal channels, and a second regionbetween the plurality of internal channels and a top that is generallyopposite the base from the plurality of internal channels. The coldplate body is made from a first thermally conductive material. The coldplate also comprises at least one thermally conductive member extendingaround the plurality of channels from the first region below theplurality of channels to the second region above the plurality ofchannels. The at least one thermally conductive member has a greatereffective thermal conductivity than the first thermally conductivematerial to move heat from the first region to the second region.

The thermally conductive members may extend from the first region of thecold plate body to the second region of the cold plate body alongvarious paths or combinations of paths. In general, the thermallyconductive members may follow any path that transfers heat from thefirst region, which is adjacent the heat generating device, to thesecond region, which is generally on the side of the plurality ofinternal channels that is opposite the first region. In this manner, theat least one thermally conductive member improves the distribution ofheat throughout the cold plate body, thereby increasing the amount ofheat that is transferred to the liquid coolant flowing through the upperportions of the internal channels. Accordingly, the cold plate is moreeffective in keeping the heat-generating component at a suitableoperating temperature.

In one optional configuration of the cold plate, one or more of thethermally conductive members has a first end that extends around a firstside of the plurality of channels and a second end that extends around asecond side of the plurality of channels. Furthermore, in such aconfiguration, the first and second ends extend through the secondregion in order to transfer heat adjacent the upper portions of theinternal channels.

In another optional configuration of the cold plate, one or more of thethermally conductive members form a loop that extends through the firstregion, around a first side of the plurality of channels, through thesecond region, and around a second side of the plurality of channels.Compared to discontinuous thermally conductive members (i.e., thosehaving two ends), the use of such loops may provide greater heattransfer area in both the first and second regions.

In yet another optional configuration of the cold plate, there are aplurality of the thermally conductive members, each having a first endin the first region and second end in the second region. In a firstoption, a first thermally conductive member may extend around a firstside of the cold plate body and a second thermally conductive member mayextend around a second side of the cold plate, wherein the first andsecond sides are adjacent sides of a generally rectangular cold plate.In a second option, a first thermally conductive member has a first endthat extends around a first side of the plurality of channels and asecond end that extends around a second side of the plurality ofchannels, and a second thermally conductive member has a first end thatextends around a third side of the plurality of channels and a secondend that extends around a fourth side of the plurality of channels.

Regardless of the path that is traversed by the at least one thermallyconductive members, the thermally conductive members may be secured to,or formed by, the cold plate body in various manners. For example, athermally conductive member may be embedded into a surface of the coldplate body with an exposed surface that is flush with the cold platesurface. Where the thermally conductive member extends along the basethrough the first region, embedding the thermally conductive member inthis manner places the member in direct thermal engagement with theheat-generating device. Accordingly, a thermally conductive member maybe embedded in the cold plate body, such as along the base, by beingreceived within an open groove formed in an exterior surface of the coldplate body. Preferably, the thermally conductive member is made toconform to the walls of the open groove for thermal engagement with thewalls. Increasing the contact area between the thermally conductivemember and the walls of the groove will increase the amount of heattransfer there between. It is also preferable that the exposed surfaceof the at least one thermally conductive member is flattened to providea flat area for thermally engaging the heat-generating device, whichpresents a flat surface area for contacting the cold plate. As onealternative to an embedded member, a thermally conductive member may besecured to an exterior surface of the cold plate body for thermallyengaging the cold plate body. Such a thermally conductive member is alsopreferably flattened to increase the contact area with the surface ofthe cold plate body.

In each of the foregoing embodiments that include a plurality ofthermally conductive members, it is preferable that each of theplurality of thermally conductive members extend into an area of thebase that thermally engages the heat generating device. For example, ifthe heat generating device is a computer processor, each of thethermally conductive members may pass into the first region adjacent theprocessor. Where the cold plate is centered over the processor, eachthermally conductive member may extend along the base of the cold platethrough a central area to thermally engage the processor. Conversely,each of the plurality of thermally conductive members is preferablyspaced apart through the second region. Such a spaced apartconfiguration in the second region is beneficial to improve thedistribution of heat throughout the second region.

The thermally conductive members may be any heat transfer device ormaterial that serves to increase the transfer of heat from the firstregion to the second region. Non-limiting examples of such thermallyconductive members include a heat pipe, a vapor chamber, a metal,graphite, and diamond. A heat pipe is a device or structure having athermally conductive outer wall forming a sealed chamber containing avolatile fluid. A vapor chamber may be formed as a structure internal tothe cold plate body without having its own discrete wall. In a specificembodiment, the first thermally conductive material is aluminum, andwherein the at least one thermally conductive member is made fromcopper. Such an embodiment is suitable, because copper has a greaterthermal conductivity than aluminum.

The cold plate will also include a liquid coolant supply line and aliquid coolant return line that are fluidically coupled to the pluralityof internal channels. It should be recognized that the liquid coolantsupply line, the liquid coolant return line, or both may be fluidicallycoupled to the plurality of internal channels through a side of the coldplate body or through the top of the cold plate body. The supply lineand return line may be located in order to avoid physical interferencewith a desired configuration of the thermally conductive members. Itshould be understood that in alternate installations the return line maybe a drain line where the liquid coolant is not reused.

The liquid coolant channels may have a cross-section that is circular,oval, elongate, or any of a plurality of other shapes. The liquidcoolant channels may also be parallel one to the others to increase theamount of surface area available for heat transfer from the cold platebody to the liquid coolant moving through the liquid coolant channels.The liquid coolant channels are preferably generally straight tominimize pressure drop within the liquid coolant flow path.

The embodiments of the present invention described herein are notlimited to any actual or relative dimensions. However, for the solepurpose of providing an example, a cold plate might have a thickness ofabout 10 mm, a width of about 75 mm, and a length of about 75 mm.

A heat pipe is a thermally conductive member forming a sealed corecontaining a fluid to transfer heat from a hot location (i.e., the firstregion) to one or more cold locations (i.e., the second region)primarily through cyclic evaporation and condensation of the fluidsealed within the core, but to a lesser extent also by conductionthrough the solid outer portion. A wick member may be disposed withinthe core to promote movement of the fluid along the core of the heatpipe. The wick, which may, for example, comprise a few layers of a finegauze, may be affixed to the inside surface of the core, such thatcapillary forces will move condensate condensed from vapor at the“condenser” portion(s) at the cold location(s) of the heat pipe throughthe wick to the “evaporator” portion(s) at the hot location(s) of theheat pipe. If the evaporator portions(s) of the heat bus are lower inelevation than the condenser portion(s), gravitational forces assist thecapillary forces within the wick. A wickless heat pipe relies ongravitational forces alone to move condensed fluid within the core fromthe condenser portion(s) to the evaporator portion(s) of the heat pipe.

The improved distribution of heat from the base to the rest of the coldplate body improves the overall cooling performance of the cold plate.Accordingly, the cold plate may have less weight and require less spacefor a given heat transfer capacity.

FIG. 1A is a perspective view of the top 12 of a cold plate 10 that hasbeen thermally enhanced with high conductivity thermal transfer paths inaccordance with one embodiment of the present invention. In thisembodiment, the cold plate 10 includes a cold plate body 12 having agrooves 14 formed in the top 16 and sides 18. Thermally conductivemembers 20 are received in the grooves 14 and conform to the walls ofthe grooves. The cold plate 10 is shown in an operable position over aheat-generating device (not shown) that is itself installed on theprinted circuit board 30. A supply line 42 and a drain/return line 44are fluidically coupled to the sides of the cold plate body for fluidcommunication with internal channels within the cold plate body.

FIG. 1B is a perspective view of the bottom of the cold plate 10 of FIG.1A in alignment with a heat-generating processor 32, which would beoperably coupled to a printed circuit board (not shown). For the purposeof cooling the processor 32, the cold plate 10 is lowered into thermalengagement with the processor. An area of contact is shown in dashedlines 34 on the base (bottom) 36 of the cold plate body 12. Thethermally conductive members 20 extend into this central region 34 forthermal engagement with the processor 32. The embedded members 20 areflush with the surface of the base 36 and are preferably flattened toincrease the contact area between the thermally conductive members 20and the processor 32. From this perspective, and in consideration ofFIG. 1, it is seen that the thermally conductive members 20 are spacedapart along the top 16 of the cold plate body to improve heatdistribution across the top of the cold plate body, but gathered intothe central region 34 along the bottom 36 of the cold plate body toimprove heat transfer with the processor 32.

FIG. 2 is a perspective view of an alternative configuration of the coldplate of FIG. 1 in alignment with a heat-generating processor. The coldplate 10A has a cold plate body 12A much the same as that of cold plate10 of FIG. 1. However, there are six thermally conductive members 20A,each having a first end that extends into the central region 34 forthermal engagement with the processor. Such an alternative configurationis completely consistent with the view in FIG. 1A.

FIG. 3 is a schematic side view of the cold plate 10 illustrating thebasic flow path of a liquid coolant through the cold plate body 12. Notethat the cold plate body is shown without the thermally conductivemember for the purpose of clarity. As shown, the liquid coolant isprovided through a supply line 42, to a supply plenum 46, throughinternal channels 47, to an output plenum 48, and then to the returnline 44.

FIG. 4 is a schematic plan view of the cold plate 10 of FIG. 3illustrating the flow path of the liquid coolant through individualchannels 47 within the cold plate 10. As described above, the liquidcoolant is provided through a supply line 42, to a supply plenum 46,through a plurality of internal channels 47, to an output plenum 48, andthen to the return line 44.

FIG. 5 is a cross-sectional view of the cold plate of FIG. 1, where thecross-section is taken through one of the thermally conductive members20. Accordingly, the base 36 of the cold plate body 12 is thermallyengaging the processor 32, which is installed on the circuit board 30. Athermally conductive member 20 extends along the base 36 and intothermal engagement with the processor 32 in the central region 34. Thethermally conductive member 20 has a first end 21 that extends around afirst side 18 of the plurality of internal channels 47 to the top 16,and a second end 23 that extends around a second side 19 of theplurality of internal channels 47 to the top 16. As a result, heat istransferred from a first region 25 between the base and the internalchannels 47 to a second region 27 between the internal channels 47 andthe top 16. Liquid coolant flowing through the internal channels 47(into the page) will, as a result of the thermally conductive member,encounter higher temperatures in adjacent the second region 27 and carryoff more heat.

FIG. 6 is a cross-sectional view of a second embodiment of a cold plate50 having a thermally conductive member 52 that extends completelyacross the top 16 of the cold plate. The thermally conductive member 52actually forms a continuous loop around the plurality of internalchannels 47. Otherwise, the thermally conductive member 52 and the coldplate 50 function in the same manner as the thermally conductive member20 and the cold plate 10 of FIG. 5.

FIG. 7 is a cross-sectional view of a third embodiment of a cold plate60 having a thermally conductive member 62 that is embedded into thecold plate body 12 along the base 36 of the cold plate, but extends incontact with the outside surfaces of the cold plate body along the sides18, 19 and top 16 of the cold plate. Otherwise, the thermally conductivemember 62 and the cold plate 60 function in the same manner as thethermally conductive member 20 and the cold plate 10 of FIG. 5.

FIG. 8A is a perspective view of the top of a cold plate 70 that hasbeen thermally enhanced with high conductivity thermal transfer paths inaccordance with another embodiment of the present invention. In coldplate 70, there is a first thermally conductive member 72 and a secondthermally conductive member 74 that form a crossing pattern on the top16 of the cold plate body 12. In order to avoid interference with thepath of the second thermally conductive member 74, the supply line 42and the return line 44 are fluidically coupled to the internal channelsthrough the top 16.

FIG. 8B is a perspective view of the bottom of the cold plate 70 of FIG.8A in alignment with a heat-generating processor 32. From this view, itcan be seen that both of the thermally conductive members 72, 74 extendinto the central region 34 to thermally engage the processor 32.However, the first thermally conductive member 72 has two ends thatextend to the top 16 (See FIG. 8A) and a second thermally conductivemember 74 has two ends that extend into the region 34.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,components and/or groups, but do not preclude the presence or additionof one or more other features, integers, steps, operations, elements,components, and/or groups thereof. The terms “preferably,” “preferred,”“prefer,” “optionally,” “may,” and similar terms are used to indicatethat an item, condition or step being referred to is an optional (notrequired) feature of the invention.

The corresponding structures, materials, acts, and equivalents of allmeans or steps plus function elements in the claims below are intendedto include any structure, material, or act for performing the functionin combination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but it is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A cold plate, comprising: a cold plate body having a base for thermally engaging a heat-generating device, a plurality of internal channels extending through the cold plate body for the passage of a liquid coolant, a first region between the base and the plurality of internal channels, and a second region between the plurality of internal channels and a top that is generally opposite the base from the plurality of internal channels, wherein the cold plate body is made from a first thermally conductive material; and at least one thermally conductive member extending around the plurality of channels from the first region below the plurality of channels to the second region above the plurality of channels, wherein the thermally conductive member has a greater thermal conductivity than the first thermally conductive material to move heat from the first region to the second region.
 2. The cold plate of claim 1, wherein the at least one thermally conductive member has a first end that extends around a first side of the plurality of channels and a second end that extends around a second side of the plurality of channels.
 3. The cold plate of claim 1, wherein the at least one thermally conductive member forms a loop that extends through the first region, around a first side of the plurality of channels, through the second region, and around a second side of the plurality of channels.
 4. The cold plate of claim 1, wherein the at least one thermally conductive member is a plurality of thermally conductive members, and wherein at least one of the plurality of thermally conductive members has a first end in the first region and second end in the second region.
 5. The cold plate of claim 1, wherein the at least one thermally conductive member is a plurality of thermally conductive members, wherein a first thermally conductive member extends around a first side of the cold plate body and a second thermally conductive member extends around a second side of the cold plate, and wherein the first and second sides are adjacent sides of a generally rectangular cold plate.
 6. The cold plate of claim 1, wherein the at least one thermally conductive member includes a first thermally conductive member and a second thermally conductive member, wherein the first thermally conductive member has a first end that extends around a first side of the plurality of channels and a second end that extends around a second side of the plurality of channels, and wherein the second thermally conductive member has a first end that extends around a third side of the plurality of channels and a second end that extends around a fourth side of the plurality of channels.
 7. The cold plate of claim 1, wherein the at least one thermally conductive member is embedded in the base with an exposed surface that is flush with the base for thermally engaging the heat-generating device.
 8. The cold plate of claim 7, wherein the at least one thermally conductive member is embedded in the base by being received within an open groove formed in an exterior surface of the cold plate body.
 9. The cold plate of claim 8, wherein the at least one thermally conductive member conforms to the walls of the open groove for thermal engagement with the walls.
 10. The cold plate of claim 8, wherein the exposed surface of the at least one thermally conductive member is flattened to provide a flat area for thermally engaging the heat-generating device.
 11. The cold plate of claim 7, wherein the at least one thermally conductive member is a plurality of thermally conductive members, and wherein each of the plurality of thermally conductive members extend into an area of the base that thermally engages the heat generating device.
 12. The cold plate of claim 11, wherein the plurality of thermally conductive members are spaced apart through the second region.
 13. The cold plate of claim 1, wherein the at least one thermally conductive member is secured to an exterior surface of the cold plate body for thermally engaging the cold plate body.
 14. The cold plate of claim 1, wherein the at least one thermally conductive member is selected from a heat pipe, a vapor chamber, metal, graphite, and diamond.
 15. The cold plate of claim 1, wherein the at least one thermally conductive member is copper.
 16. The cold plate of claim 1, wherein the at least one thermally conductive member is a heat pipe having a thermally conductive outer wall forming a sealed chamber containing a volatile fluid.
 17. The cold plate of claim 1, wherein the first thermally conductive material is aluminum, and wherein the at least one thermally conductive member is made from copper.
 18. The cold plate of claim 1, wherein the first thermally conductive material is selected from aluminum and copper, and wherein the at least one thermally conductive member is a heat pipe.
 19. The cold plate of claim 1, further comprising: a liquid coolant supply line and a liquid coolant return line that are fluidically coupled to the plurality of internal channels.
 20. The cold plate of claim 19, wherein the liquid coolant supply line, the liquid coolant return line, or both are fluidically coupled to the plurality of internal channels through a side of the cold plate body.
 21. The cold plate of claim 19, wherein the liquid coolant supply line, the liquid coolant return line, or both are fluidically coupled to the plurality of internal channels through the top of the cold plate body. 